honorifics - Is there a rule for using or not using the definite article before people’s titles?

The use of the definite article before titles is a confusing area - I always hear “Queen Elizabeth visited” and never “The Queen Elizabeth visited”. But I always hear “The Prince of Wales visited” and never “Prince of Wales visited”.

Is there a rule for using — or not using — the definite article before people’s titles?

Answer

In certain cases and contexts these are virtual proper names of persons. It should be Her Majesty The Queen. This is why you get The Prince of Wales, The Archbishop of Canterbury, The President of the United States.. etc.

So if you were referring to Prince Charles, it would be Prince Charles, The Prince of Wales, not The Prince Charles. If you referred to his title it would be The Prince of Wales.

So The applies to the title, not necessarily the person but it depends on case and context.